Conventional technology pertaining to certain embodiments of the present invention is described in the following publications inter alia:
Apparatus and methods for generating pressure waves are known e.g. from co-pending published PCT application WO 2007/135680; digital speaker devices are known e.g. from co-pending published PCT application WO 2009/066290.
Conventional noise shaping also termed sigma-delta modulation and delta-sigma modulation is described in “Understanding Delta-Sigma Data Converters” by Richard Schreier and Gabor C. Temes.
The disclosures of all publications and patent documents mentioned in the specification, and of the publications and patent documents cited therein directly or indirectly, are hereby incorporated by reference.